Foam core article with flexible heat-resistant knitted fabric

ABSTRACT

A foam core article such as a mattress or pillow is covered on a surface with a flexible heat-resistant knitted fabric. Preferably a further sacrificial fabric also is used to allow passage of CPSC 16 CFR 1633 with a peak heat release of no more than 200 kilowatts in a 30 minute time period following ignition.

RELATED APPLICATION

The present patent application is a continuation-in-part of Ser. No.11/897,581 file Aug. 31, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is directed to an article having a foam core such as amattress or pillow in combination with a flexible heat-resistant knittedfabric. In a preferred embodiment the invention also employs asacrificial fabric.

2. Description of Related Art

The State of California has led the drive to regulate and reduce theflammability of mattresses and mattress sets in an attempt to reduce thenumber of lives lost in household, hotel, and institutional fires. Inparticular, the Bureau of Home Furnishings and Thermal Insulation of theDepartment of Consumer Affairs of the State of California issuedTechnical Bulletin 603 “Requirements and Test Procedure for Resistanceof a Residential Mattress/Box Spring Set to a Large Open-Flame” toquantify the flammability performance of mattress sets.

A further test procedure to determine the suitability of a mattressconstruction with a fire barrier is set forth in test procedure CPSC 16CFR1633.

A mattress normally contains a mattress core covered by cushioningmaterial or batting that is in turn covered with an outer fabricticking. Most cushioning material or batting is made from foam or fibermaterials that will burn when exposed to an open flame. Therefore asubstantial effort has been made to cover a mattress with a fireresistant barrier to conform to flammability regulations.

A need is present for an improved fire barrier material and improvedconstruction which retard burning of an article having a foam core.

SUMMARY OF INVENTION

The present invention in a preferred mode is directed to a mattress witha flexible heat-resistant knitted fabric comprising:

(I) a mattress having a foam core and

(II) a flexible heat-resistant knitted fabric covering at least aportion of a surface of the mattress wherein the knitted fabriccomprises:

(a) para-aramid yarn; and

(b) cellulosic yarn wherein cellulosic material in the yarn has not beentreated to improve fire resistance, with the provisos:

(i) the para-aramid is present in an amount of at least 38 percent byweight of the knitted fabric on a basis of para-aramid and cellulosicmaterial in the yarns,

(ii) the para-aramid yarn has a size in a range from 45 cc to 20 cc,

(iii) the cellulosic yarn has a size in a range from 45 cc to 20 cc and

(iv) the knitted fabric has a stitch density in a range from 300 to 700stitches per square inch.

Also the present invention is directed to other articles with a foamcore article with an example being a pillow or other furniturecushioning.

In a most preferred embodiment a sacrificial fabric is employed with thefoam core article and the flexible heat-resistant knitted fabric.

DETAILED DESCRIPTION OF THE INVENTION

A preferred substrate of the present invention is a mattress having afoam core. Due to the flammability of the foam an added degree ofprotection is needed to resist burning particularly since a mattress mayinclude more than one layer of foam with different densities, differentmaterials and different degrees of resiliency. The mattress may or maynot contain springs for resiliency. In a preferred embodiment, themattress does not contain springs which conventionally denotes a needfor a larger mass of foam.

In the present invention the mattress is at least partially covered onits outer surface (i.e. a surface which faces an observer) with aflexible heat-resistant knitted fabric. The knitted fabric containspara-aramid yarn and cellulosic yarn. The cellulosic material is nottreated to impart fire resistance and accordingly does not impart anadded degree of fire resistance to the yarn compared to a cellulosicmaterial with, for example, a fire resistant chemical.

The para-aramid is present in an amount of at least 38 percent by weighton a basis of para-aramid and cellulosic material in the knitted fabric.Preferably the para-aramid will be at least 40 percent on this basis.Accordingly the weight ranges are 38 to 60 percent para-aramid andcorrespondingly 40 to 62 percent cellulosic material. A more preferredrange is 40 to 60 percent para-aramid and 40 to 60 percent cellulosicmaterial.

For purposes of the present invention, the following definitions areemployed.

As employed herein a foam core denotes a resilient material having gasbubbles entrapped therein

Knitted fabric denotes a fabric which is knitted with yarns containingpara-aramid and yarns containing cellulosic material wherein the yarnsare intermixed in the fabric, i.e. the yarns do not lie in separatelayers such as one fabric layer containing only para-aramid yarns andanother separate layer containing only cellulosic material.

As used herein “cellulosic” and “cellulosic material” includes cotton,rayon and combinations. However this definition is employed to excludecellulosic materials which have been treated for the purpose impartingflame resistance (FR). According FR cotton and FR rayon are excluded incalculating the above-stated weight percentage requirements.

The knitted fabric containing para-aramid yarns and cellulosic yarnsimparts heat resistance such as from a flame (in air) due to an abilityto retard burning for a period of time. This resistance is present eventhough the cellulosic material can readily burn.

However a further criteria for the heat-resistant knitted fabric is anability to have flexibility and a degree of stretch. Illustratively theheat-resistant knitted fabric typically will cover one surface of amattress with wrapping of the fabric around corners of the mattress. Apreferred use is where the fabric covers all exterior mattress surfaces.The flexibility and stretch of the heat-resistant knitted fabric allowssuch use.

The flexibility and stretch of the heat-resistant knitted fabric isimparted by use of para-aramid yarn and cellulosic yarn within aspecific size range as well as within a specific stitch density range.Both the para-aramid yarn and the cellulosic yarn will have a size in arange from 45 cc to 20 cc (cc means cotton count in accordance withstandard nomenclature). A preferred range for both yarns is 45 cc to 20cc. Although a single ply yarn is preferred, it is understood that morethan one ply may be employed in a yarn. The knitted fabric has a stitchdensity in a range from 300 to 700 stitches per square inch (47 to 109stitches per square centimeter). A preferred range is 400 to 600stitches per square inch (62 to 93 stitches per square centimeter).

The weave of the flexible heat-resistant knitted fabric is not criticalprovided the above criteria are present. Examples of suitable knittedfabrics include jersey (or single) knits, rib (or double) knits, terryknits and French terry knits.

In a preferred embodiment an article resulting from a mattress andflexible heat-resistant knitted fabric will pass CPSC 16 CFR1633 whichis a burning test. Accordingly in conformance with this test a maximumheat peak release is necessary, namely no more than 200 kilowatts in a30 minute time period following ignition.

In order to pass this test in the present invention a sacrificial fabricis needed in combination with the mattress and flexible heat-resistantknitted fabric wherein the sacrificial fabric faces a heat sourceemployed in the test procedure. The sacrificial fabric denotes amaterial which burns in the test. The material typically employed is acotton fabric.

To determine in a mattress and flexible heat-resistant knitted fabricwill pass CPCS 16 CFR1633 with a peak heat release of no more than 200kilowatts in a 30 minute time period, a terry cloth cotton fabric(untreated for fire resistance) is employed on a weight basis of 8ounces per square yard and use of such fabric is denoted herein as “testprocedure A” which is useful for screening purposes. It is understood inactual use by a consumer that another sacrificial fabric and/or anotherweight may be and would be expected to be used.

Although the above description of the invention is directed to amattress with a foam core, it is understood that other materials whichuse a foam core are suitable. An example is a pillow or other furniturecushioning.

To further illustrate the present invention, the following examples areprovided. All parts and percentages are by weight unless otherwiseindicated.

COMPARATIVE EXAMPLE A

In Comparative Example A, a foam core mattress made from a 8 ounces persquare yard terry knit cover fabric comprising cotton and polyesteryarns available from A Lava and Sons, Chicago, Ill., a flame resistant,circular, jersey knit barrier comprising co-fed 18 s/1 cotton yarnavailable from Parkdale Mills, Gastonia, N.C. and 45 s/1 Kevlar yarnavailable from Charles Craft, Inc., Laurinburg, N.C. (equivalent to a29% Kevlar, 71% cotton blend of yarns), and a foam core comprising a 3inch visco-elastic polyurethane foam layer and a 7 inch densepolyurethane foam layer available from Leggett and Platt, Inc., Chicago,Ill. were collected. The foam core mattress was produced by insertingthe foam core into the flame resistant, circular, jersey knit barrier,each end of the jersey knit tube was sewn closed with 60 Tex Kevlarthread available from Coats and Clark, Charlotte, N.C., and finallyinserting the flame resistant, jersey knit covered foam core into theterry knit cover fabric. The foam core mattress was then tested foroverall mattress flammability per CPSC standard 16 CFR 1633. The foamcore mattress had the following results: Two out of three foam coremattress sets failed the CPSC 16 CFR 1633 flammability standard bymeasuring a peak heat release rate of greater than 200 kW in the first30 minutes after ignition. See Table 1.

EXAMPLE 1

In Example 1, a foam core mattress made from a 8 ounces per square yardterry knit cover fabric comprising cotton and polyester yarns availablefrom A Lava and Sons, Chicago, Ill., a flame resistant, circular, jerseyknit barrier comprising co-fed 30 s/1 cotton yarn available fromParkdale Mills, Gastonia, N.C. and 30 s/1 Kevlar yarn available fromCharles Craft, Inc., Laurinburg, N.C. (equivalent to a 50% Kevlar, 50%cotton blend of yarns), and a foam core comprising a visco-elasticpolyurethane foam layer and a dense polyurethane foam layer availablefrom Leggett and Platt, Inc., Chicago, Ill. were collected. The foamcore mattress was produced by inserting the foam core into the flameresistant, circular, jersey knit barrier, each end of the jersey knittube was sewn closed with 60 Tex Kevlar thread available from Coats andClark, Charlotte, N.C., and finally inserting the flame resistant,jersey knit covered foam core into the terry knit cover fabric. The foamcore mattress was then tested for overall mattress flammability per CPSCstandard 16 CFR 1633. The foam core mattress had the following results:three foam core mattress sets passed the 16 CFR 1633 test requirementsthat included a heat release rate of no more than 200 kW in the first 30minutes after ignition and a total heat release of no more than 15 MJ inthe first 10 minutes after ignition. See Table 1.

EXAMPLE 2

In Example 1, a foam core mattress made from a 8 ounces per square yardterry knit cover fabric comprising cotton and polyester yarns availablefrom A Lava and Sons, Chicago, II, a flame resistant, circular, jerseyknit barrier comprising co-fed 30 s/1 cotton yarn available fromParkdale Mills, Gastonia, N.C. and 45 s/1 Kevlar yarn available fromCharles Craft, Inc., Laurinburg, N.C. (equivalent to a 40% Kevlar, 60%cotton blend of yarns), and a foam core comprising a visco-elasticpolyurethane foam layer and a dense polyurethane foam layer availablefrom Leggett and Platt, Inc., Chicago, Ill. were collected. The foamcore mattress was produced by inserting the foam core into the flameresistant, circular, jersey knit barrier, each end of the jersey knittube was sewn closed with 60 Tex Kevlar thread available from Coats andClark, Charlotte, N.C., and finally inserting the flame resistant,jersey knit covered foam core into the terry knit cover fabric. The foamcore mattress was then tested for overall mattress flammability per CPSCstandard 16 CFR 1633. The foam core mattress had the following results:two foam core mattress sets passed the 16 CFR 1633 test requirementsthat included a heat release rate of no more than 200 kW in the first 30minutes after ignition and a total heat release of no more than 15 MJ inthe first 10 minutes after ignition. The one sample failure was causedby the incorporation of a head to toe seam in the flame resistant,jersey knit barrier. This seam was included for the express purpose ofcreating a flame resistant, jersey tube for full scale mattress testing.This seam will not be apart of the proposed final product and thus thisblend of Kevlar® and cotton fiber is considered to pass the CPSCstandard 16 CFR 1633. See Table 1.

TABLE 1 FR Mattress CPSC 16 CFR 1633 Test Results Comparative Example AExample 1 Example 2 Barrier Co-fed 29% Kevlar, Co-fed 50% Kevlar, Co-fed40% Kevlar, 71% Cotton circular, 50% Cotton circular, 60% Cottoncircular, jersey knit jersey knit jersey knit Foam Core Visco-elasticfoam Visco-elastic foam top Visco-elastic foam Construction top withpolyurethane with polyurethane top with polyurethane foam base foam basefoam base Cover Fabric Knit 60% Cotton, 40% 60% Cotton, 40% 60% Cotton,40% Composition polyester polyester polyester Peak HRR (kW) in 178.1*39.8 42.9 30 min 40.9 39.7 256.6** 539 41.6 99.8 Total Heat Release 8.4*12.1 5.9 (MJ) in 10 min 6.7 10.4 17.5** 9.9 5.3 10.7 *Test stopped forsafety reasons due to samples imminent failure. **Test failed due to aseam in the barrier incorporated for purpose of testing. This head totoe seam is not intended to be apart of the final mattress construction.

1. An article of a mattress with a flexible heat-resistant knittedfabric comprising: (I) a mattress having a foam core; and (II) aflexible heat-resistant knitted fabric covering at least a portion of asurface of the mattress wherein the knitted fabric comprises: (a)para-aramid yarn; and (b) cellulosic yarn wherein cellulosic material inthe yarn has not been treated to improve fire resistance, with theprovisos: (i) the para-aramid is present in an amount of at least 38percent by weight of the knitted fabric on a basis of para-aramid andcellulosic material in the yarns, (ii) the para-aramid yarn has a sizein a range from 45 cc to 20 cc, (iii) the cellulosic yarn has a size ina range from 45 cc to 20 cc and (iv) the knitted fabric has a stitchdensity in a range from 300 to 700 stitches per square inch.
 2. Thearticle of claim 1 wherein, the mattress does not contain springs. 3.The article of claim 1 wherein, the para-aramid is poly(paraphenyleneterepthalamide).
 4. The article of claim 1 wherein, the cellulosicmaterial is cotton or rayon.
 5. The article of claim 4 wherein, thecellulosic material is cotton.
 6. The article of claim 1 wherein, thepara-aramid yarn has a size in a range from 40 cc to 24 cc and thecellulosic yarn has a size in a range from 40 cc to 24 cc and theknitted fabric has a stitch density in a range from 400 to 500 stitchesper square inch.
 7. The article of claim 1, which additionally containsa sacrificial fabric with a construction in order (a) mattress, (b)flexible heat-resistant knitted fabric and (c) sacrificial fabric,wherein, the article passes CPSC 16 CFR1633 with a peak heat release ofno more than 200 kilowatts in a 30 minute time period after ignition. 8.The article of claim 7 wherein, the sacrificial fabric comprises cotton.9. An article comprising in order: (I) a foam core, (II) a flexibleheat-resistant knitted fabric covering at least a portion of a surfaceof the foam core wherein the knitted fabric comprises (a) para-aramidyarn and (b) cellulosic yarn wherein cellulosic material in the yarn hasnot been treated to improve fire resistance, with the provisos: (i) thepara-aramid is present in an amount of at least 38 percent by weight ofthe knitted fabric on a basis of para-aramid and cellulosic material inthe yarns, (ii) the para-aramid yarn has a size in a range from 45 cc to20 cc, (iii) the cellulosic yarn has a size in a range from 45 cc to 20cc and (iv) the knitted fabric has a stitch density in a range from 300to 700 stitches per square inch and (III) a sacrificial fabric, with theproviso the article passes CPSC 16 CFR1633 with a peak heat release ofno more than 200 kilowatts in a 30 minute time period after ignition.10. The article of claim 9 wherein, the sacrificial fabric comprisescotton.